Resealable film

ABSTRACT

The present invention relates to a resealable container comprising: a polyethylene terephthalate-based container body comprising a bottom side and at least one upwardly extending sidewall, wherein the sidewall terminates in an open end of the container; a flexible film sealed to the container body, over the open end of the container, wherein the flexible film comprises: a polyethylene-based first film layer; a pressure sensitive adhesive layer adjacent a lower surface of the first film layer; a polyolefin plastomer skin layer adjacent a lower surface of the pressure sensitive adhesive layer, wherein the first layer, pressure sensitive adhesive layer, and skin layer are coextruded; and a heat seal layer printed onto a lower surface of the skin layer and heat sealed to the container body.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.16/568,491, filed on Sep. 12, 2019, entitled “RESEALABLE FILM”, which isincorporated herein in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to a resealablepolyethylene-based film for use with containers comprising polyethyleneterephthalate.

SUMMARY OF THE INVENTION

In an embodiment, the invention is directed to a polyethylene-(PE)based, resealable, coextruded (COEX) film which is adhered to a rim,edge, or flange of a rigid container which comprises polyethyleneterephthalate (PET), including amorphous polyethylene terephthalate(APET).

In an embodiment, the invention is directed to a resealable containercomprising: a polyethylene terephthalate-based container body comprisinga bottom side and at least one upwardly extending sidewall, wherein thesidewall terminates in an open end of the container; a flexible filmsealed to the container body, over the open end of the container,wherein the flexible film comprises: a polyethylene-based first filmlayer; a pressure sensitive adhesive layer adjacent a lower surface ofthe first film layer; a polyolefin plastomer skin layer adjacent a lowersurface of the pressure sensitive adhesive layer, wherein the firstlayer, pressure sensitive adhesive layer, and skin layer are coextruded;and a heat seal layer printed onto a lower surface of the skin layer andheat sealed to the container body.

In another embodiment, the invention is directed to a resealablecontainer comprising: an amorphous polyethylene terephthalate containerbody comprising a bottom side and at least one upwardly extendingsidewall, wherein the sidewall terminates in an open end of thecontainer; a flexible film sealed to the container body, over the openend of the container, wherein the flexible film comprises: a highdensity polyethylene first film layer; a pressure sensitive adhesivelayer adjacent a lower surface of the first film layer; anethylene-vinyl acetate skin layer adjacent a lower surface of thepressure sensitive adhesive layer; and a heat seal layer adjacent alower surface of the skin layer and heat sealed to the container body.

A method of making a resealable container comprising: providing apolyethylene terephthalate-based container body comprising a bottom sideand at least one upwardly extending sidewall, wherein the sidewallterminates in an open end of the container; coextruding a flexible filmcomprising: a polyethylene-based first film layer; a pressure sensitiveadhesive layer adjacent a lower surface of the first film layer; apolyolefin plastomer skin layer adjacent a lower surface of the pressuresensitive adhesive layer; printing a heat seal layer adjacent a lowersurface of the skin layer to form a heat-sealable film; and heat sealingthe heat-sealable film to the container body, over the open end of thecontainer.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendeddrawings, in which:

FIG. 1 illustrates an exploded cross-sectional embodiment of the filmand container of the invention shown in a closed configuration;

FIG. 2 illustrates an exploded cross-sectional embodiment of the filmand container of the invention shown in an open configuration; and

FIG. 3 illustrates a cross-sectional embodiment of the film andcontainer of the invention shown in a closed configuration.

Elements illustrated in the figures are not necessarily drawn to scale.Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference will now be made in detail to embodiments of the invention,one or more examples of which are illustrated in the accompanyingdrawings. Each example is provided by way of explanation of theinvention, not limitation of the invention. In fact, it will be apparentto those skilled in the art that modifications and variations can bemade in the present invention without departing from the scope or spiritthereof. For instance, features illustrated or described as part of oneembodiment may be used on another embodiment to yield a still furtherembodiment. Thus, it is intended that the present invention covers suchmodifications and variations as come within the scope of the appendedclaims and their equivalents.

In an embodiment, the invention comprises a heat-sealable, peelable andresealable multilayer lidding film. The lidding film may be useful forsealing containers which contain food products such as fresh fruit andproduce, pharmaceuticals, personal care products, chemical products,cleaning products, or any other products known in the art. In anembodiment, the products may be consumed or used over time and mayrequire multiple container opening and resealing processes. In aparticular embodiment, the film may be useful for sealing containersthat comprise a molded or shaped container defining a cavity. Thecontainer of the invention may have a bottom and one or more sides. Thecontainer body may contain one or more vents which allow ventilation oroff-gassing. The container bottom and at least one sidewall may definethe cavity. The one or more sides may terminate in an edge, rim, orflange. The container may be PET-based, in an embodiment.

In conventional resealable coextruded films (i.e. a coextruded filmcomprising a resealable adhesive), the film layer(s) are made from apolyethylene-based material. Unfortunately, however, polyethylene-basedcoextruded films will only seal to PE-based or polypropylene-(PP) basedcontainers and will not seal to PET-based containers. In fact, theinventor is not aware of any resealable coextruded films that aresealable to amorphous PET containers, for example. Further, a heat sealcoating that may otherwise allow adhesion to a PET-based containercannot be printed onto a standard coextruded PE films because those PEfilms are not print-receptive, particularly to a PET-compatible heatseal. Thus, heretofore, there has been no solution which would allowheat-sealing a coextruded PE-based film onto a PET-based container.Through hard work and ingenuity, the inventors have developed acoextruded PE-based film structure which comprises a skin layer that isreceptive to a PET-based heat seal coating. The coextruded PE filmstructure will split at the designated failure location, exposing apressure sensitive adhesive (PSA) extrudate for reseal purposes.

Turning to the drawings, FIGS. 1 and 2 illustrate explodedcross-sectional views of the film 10 of the invention. The film 10 maybe applied to a container 20. In an embodiment, the film 10 may beapplied to an edge, rim, or flange 22 of a container 20. In anembodiment, the film 10 may be applied to the top surface 24 of theflange 22.

In an embodiment, the film 10 comprises a multilayer structure. In aparticular embodiment, the first or outermost layer 12 of the filmstructure 10 may comprise a PE-based material. As used herein, the term“PE-based” may include high density polyethylene (HDPE), low densitypolyethylene (LDPE), medium density polyethylene (MDPE), ultra highmolecular weight polyethylene (UHMWPE), cross-linked polyethylene (PEX),linear low density polyethylene (LLDPE), very low density polyethylene(VLDPE), polyethylene copolymers, chemically-modified polyethylene,and/or any other PE-based film material. Any polyethylene material knownin the art may be utilized in the invention. In an embodiment, aPE-based material comprises any material with the chemical formula(C₂H₄)_(n). In an embodiment, the first layer 12 may comprise aplurality of layers.

In an embodiment, directly adjacent the first layer 12 is a PSA layer14. The PSA layer 14 may be coextruded with the first layer 12, in anembodiment. In other embodiments, the PSA layer 14 may be separatelyapplied to the underside of the first layer 12, such as at an adhesivestation. In one embodiment, the PSA layer 14 may be pattern applied tothe first layer 12. In another embodiment, the PSA layer 14 may becontinuous across and/or coextensive with the first layer 12. Any PSAknown in the art may be utilized as the PSA layer 14.

In an embodiment, a skin layer 16 may be disposed on the opposite sideof the PSA layer 14 from that of the first layer 12. In an embodiment,the skin layer 16 is disposed on the underside of the first layer 12,with respect to the container interior, adhered to the first layer 12via the PSA layer 14. In an embodiment, the skin layer 16 is coextrudedwith the first layer 12 and the PSA layer 14. The coextruded, multilayerfilm of the present invention, in some embodiments, can advantageouslybe coextruded in a single step. In some embodiments, the coextruded,multilayer film is a blown film; in other embodiments, the coextruded,multilayer film is a cast film. In another embodiment, the skin layer 16is extrusion coated onto the combined first layer 12 and PSA layer 14.In an embodiment, the skin layer 16 is coextensive with the dimensionsof the first layer 12.

The skin layer 16, in an embodiment, has a low seal initiationtemperature. In an embodiment, the skin layer 16 comprises a polyolefinplastomer. In an embodiment, the skin layer 16 comprises ethylene-vinylacetate (EVA). In an embodiment, the skin layer 16 comprises a low sealinitiation copolymer that is print receptive. In an embodiment, the skinlayer 16 may comprise a long-chain branched, metallocene-catalyzedhomogeneous ethylene/alpha-olefin copolymer.

As used herein, the term “polyolefin” refers to olefin polymers andcopolymers, especially ethylene and propylene polymers and copolymers,and to polymeric materials having at least one olefinic comonomer, suchas ethylene vinyl acetate copolymer and ionomer. Polyolefins can belinear, branched, cyclic, aliphatic, aromatic, substituted, orunsubstituted. Included in the term polyolefin are homopolymers ofolefin, copolymers of olefin, copolymers of an olefin and a non-olefiniccomonomer copolymerizable with the olefin, such as vinyl monomers,modified polymers of the foregoing, and the like. Modified polyolefinsinclude modified polymers prepared by copolymerizing the homopolymer ofthe olefin or copolymer thereof with an unsaturated carboxylic acid,e.g., maleic acid, fumaric acid or the like, or a derivative thereofsuch as the anhydride, ester metal salt or the like. It could also beobtained by incorporating into the olefin homopolymer or copolymer, anunsaturated carboxylic acid, e.g., maleic acid, fumaric acid or thelike, or a derivative thereof such as the anhydride, ester metal salt orthe like.

In an embodiment, the skin layer 16 may comprise up to about 15% of thetotal thickness of the film 10 structure. In an embodiment, the totalthickness of the film structure is between about 1.5 and 2.5 mils. Insome embodiments, the skin layer 16 may contain various polymersdesigned to weaken the affinity of the skin layer 16 for the PSA layer.In an embodiment, the skin layer 16 may be corona treated.

In an embodiment, a heat seal layer 18 is disposed adjacent the skinlayer 16, opposite the PSA layer 14. The heat seal layer 18 may beprinted onto the underside of the skin layer 16, in an embodiment. Anyheat seal material known in the art may be utilized in this embodiment.In an embodiment, the heat seal material may comprise a thermallyactivatable adhesive composition, such as a hot melt adhesive resin. Inan embodiment, the heat seal layer 18 provides the film with the abilityto be heat-sealed to trays, containers, or other substrates. In anembodiment, the heat seal layer 18 may comprise a heat seal materialwhich is compatible with sealing to a PET-based container, such as anAPET container. In an embodiment, the heat seal layer 18 may comprise apolymeric material. In some embodiments, the heat seal layer 18 and thecontainer 20 may comprise the same polymeric composition. Thus, in someaspects, both the heat seal layer 18 and the container 20 may compriseAPET. In some embodiments, the heat seal layer 18 comprises PET and thecontainer 20 may comprise APET.

As used herein, the term “heat seal” refers to the union of twomaterials by bringing the materials into contact, or at least closeproximity, with one another and then applying sufficient heat and,optionally, pressure to a predetermined area (or areas) of the materialsto cause the contacting surfaces of the materials in the predeterminedarea to become molten and intermix with one another, thereby forming anessentially inseparable bond between the two materials in thepredetermined area when the heat and, optionally, pressure are removedtherefrom and the area is allowed to cool. In accordance with anembodiment of the present invention, a heat seal preferably creates ahermetic seal, i.e., a barrier to the outside atmosphere.

In an embodiment, the container 20 is a PET-based container, such asPET, APET, crystallized polyethylene terephthalate (CPET), reinforcedpolyethylene terephthalate (RPET), glycol-modified polyethyleneterephthalate (PETG), isophthalic acid (iPET), oriented PET, or anyother PET copolymer or other PET-based material known in the art. In aparticular embodiment, the container 20 comprises APET.

In an embodiment, the film 10 may be heat sealed to the edge or rim ofthe container 20. In one embodiment, the film 10 may be heat sealed tothe flange 22 on at least one side, e.g., on all four sides of thecontainer 20. The container 20 may have a recessed portion and a flange22. The recessed portion may define a product-receiving cavity. Theflange 22 may comprise two opposing edges with the width of thecontainer 20 separating the two. In an embodiment, the film 10 extendsacross the cavity and is sealed and attached on at least one side, e.g.,on all four sides, of the flange 22. After an initial opening of thefilm 10 such as by a consumer, the lidding may be resealed against theflange 22 and retained closed by the PSA layer 14.

More specifically, in an embodiment shown in FIG. 2 , when the film 10is peeled away from the container 20, a break occurs between the PSAlayer 14 and the skin layer 16. That is, the adhesion and/or affinitybetween the skin layer 16 and the heat seal layer 18 is greater thanthat between the skin layer 16 and the PSA layer 14. The peel strengthto break the bond between the heat seal layer 18 and the skin layer 16may be greater than the peel strength to break the bond between the skinlayer 16 and the PSA layer 14. The PSA layer 14 is retained on the firstlayer 12 and lifts away from the container 20.

In an embodiment, the skin layer 16 will bond to the surface of theflange 22 with the heat seal layer 18. In this embodiment, the film 10may fracture at the interface of the skin layer 16 and the PSA layer 14when the lidding is opened, exposing the extruded pressure sensitivelayer 14 for reseal. In another embodiment, the film 10 may fracture atthe interface of the first layer 12 and the PSA layer 14 when thelidding is opened, exposing the extruded pressure sensitive layer 14 forreseal. In still another embodiment, the film 10 may fracture internalto the PSA layer 14 when the lidding is opened, exposing some of theextruded pressure sensitive layer 14 for reseal on one or both of thefirst layer 12 and the skin layer 16.

In an embodiment, a reseal surface 30 may be created on the underside ofthe first layer 12 or the upper side of the skin layer 16, due to thePSA layer 14. The reseal surface 30 comprises exposed PSA and can berepeatedly re-adhered to the flange 22. In an embodiment, there-adherence of the first layer 12 to the flange 22 comprises resealingthe first layer 12 to the skin layer 16, via the PSA layer 14.

In one embodiment, a corner of the film 10 overhangs at least a portionof the flange 22, e.g., at one or more corners. The overhang(s) mayfacilitate removal of the film 10 from container 20.

In an embodiment, the layers of the film 10 of the invention comprise,in this order: HDPE layer 12, PSA layer 14, skin layer 16, heat seallayer 18. In an embodiment, the film 10 is heat sealed to an APETcontainer 20. FIG. 4 illustrates a cross-sectional view of a container20 of the invention, wherein the container 20 contains a food product 32and is closed via a film 10 of the invention.

In an embodiment, the film 10 may comprise microperforations ormacroperforations, and may be mechanically or laser-scored. In anembodiment, the container 20 may be utilized for storage of fresh fruitand produce. In an embodiment, the container 20 may contain perforationsor vents.

The accompanying figures are provided for explanatory purposes and maynot show the different layers, plies, adhesives, labels, inks, barriers,and other components described above with respect to embodiments of thecontainer. In addition, those components that are illustrated are notnecessarily drawn to scale. Thus, certain layers that are shown as thesame thickness or thinner than other layers may actually be thicker thanother layers, and so on.

Many modifications and other embodiments of the inventions set forthherein will come to mind to one skilled in the art to which theseinventions pertain having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the inventions are not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

What is claimed is:
 1. A flexible film comprising: a polyethylene-basedfirst film layer; a pressure sensitive adhesive layer adjacent a lowersurface of the first film layer; a polyolefin plastomer skin layeradjacent a lower surface of the pressure sensitive adhesive layer,wherein the first layer, pressure sensitive adhesive layer, and skinlayer are coextruded; and a heat seal layer printed onto a lower surfaceof the skin layer.
 2. The flexible film of claim 1, wherein thepolyethylene-based first film layer comprises high density polyethylene.3. The flexible film of claim 1, wherein the skin layer isprint-receptive.
 4. The flexible film of claim 1, wherein the skin layerhas a low seal initiation temperature.
 5. The flexible film of claim 1,wherein the skin layer comprises ethylene-vinyl acetate.
 6. The flexiblefilm of claim 1, wherein the skin layer is corona treated.
 7. Theflexible film of claim 1, wherein the at least one sidewall terminatesin an edge and the flexible film is adhered to the edge.
 8. The flexiblefilm of claim 1, wherein the at least one sidewall terminates in aflange and the flexible film is adhered to the flange.
 9. The flexiblefilm of claim 1, wherein the heat seal layer comprises a hot meltadhesive resin.
 10. The flexible film of claim 1, additionallycomprising a polyethylene terephthalate-based container body sealed tothe heat seal layer of the flexible film.
 11. The flexible film of claim10 wherein the polyethylene terephthalate-based container body comprisesamorphous polyethylene terephthalate.
 12. The flexible film of claim 10wherein the container body comprises a base and at least one sidewallextending upwardly from the base, wherein the sidewall terminates in anedge defining an opening, and wherein the flexible film is adhered tothe edge.
 13. The flexible film of claim 10 wherein the container bodycomprises a base and at least one sidewall extending upwardly from thebase, wherein the sidewall terminates in a flange defining an opening,and wherein the flexible film is adhered to the flange.
 14. Thecontainer of claim 10, wherein when the flexible film is peeled awayfrom the container body, a fracture occurs between the pressuresensitive adhesive layer and the skin layer, between the first filmlayer and the pressure sensitive adhesive layer, or within the pressuresensitive adhesive layer.
 15. The container of claim 10, wherein whenthe flexible film is peeled away from the container body, the skin layerremains sealed to the container body.
 16. A flexible film comprising: ahigh density polyethylene first film layer; a pressure sensitiveadhesive layer adjacent a lower surface of the first film layer; anethylene-vinyl acetate skin layer adjacent a lower surface of thepressure sensitive adhesive layer; and a heat seal layer adjacent alower surface of the skin layer.
 17. The flexible film of claim 16additionally comprising an amorphous polyethylene terephthalatecontainer body having a base and at least one upwardly extendingsidewall, wherein the sidewall terminates in an open end of thecontainer, and wherein the heat seal layer of the flexible film issealed to the open end of the container.
 18. The flexible film of claim17, wherein when the flexible film is peeled away from the containerbody, a fracture occurs between the pressure sensitive adhesive layerand the skin layer, between the first film layer and the pressuresensitive adhesive layer, or within the pressure sensitive adhesivelayer.
 19. The container of claim 17, wherein when the flexible film ispeeled away from the container body, the skin layer remains sealed tothe container body.
 20. The container of claim 17, wherein thepolyethylene terephthalate-based container body comprises amorphouspolyethylene terephthalate.
 21. The container of claim 17, wherein thepolyethylene-based first film layer comprises high density polyethylene.22. The container of claim 17, wherein the skin layer comprisesethylene-vinyl acetate.